Liaquat Husain

Measurements of gaseous HONO, HNO3, SO2, HCl, NH3, particulate sulfate and PM2.5 in New York, NY

Simultaneous measurements of gaseous HONO, HNO3, HCl, SO2, and NH3 for a period of 1 year from July 1999 to June 2000 and fine-fraction particulate (<2.5 μm) sulfate (SO42−) from January 1999 to November 2000 were made at Bronx and Manhattan in New York City with an annular denuder system followed by ion chromatography. The hourly PM2.5 mass was measured with a Rupprecht and Patashnick TEOM Series 1400a real-time monitor for approximately 2 years (January 1999–November 2000) at the same sites. Concentrations at the two sites were highly correlated, with Manhattan being slightly higher than at the Bronx. The concentrations of HNO3, HCl, NH3 and SO42− were higher during summer than winter, the summer/winter ratios at Manhattan being 3.9, 3.1, 1.5, and 1.9, respectively. The concentrations of HONO and SO2 were lower during summer than winter, the summer/winter ratios at Manhattan being 0.48 and 0.44, respectively. Gaseous HONO concentrations were higher than that of HNO3 except in summer, when the HNO3 was higher. The annual mean concentration of PM2.5 was 15.2 μg/m3 at the Bronx, and 15.5 μg/m3 at Manhattan (based only on days when data were available from both sites). The monthly mean concentrations at Manhattan ranged from 13.2 to 21.7 μg/m3 and were highest in June and July 1999, and lowest in March and April. The monthly mean fraction of PM2.5 as SO42− ranged from 0.17 to 0.31, with the highest values observed during June–September. The hourly mean concentrations of PM2.5 showed a bimodal pattern, with peaks at around 7–8 AM and 8–9 PM. In general, the second maximum is lower than the morning one, but during summer this is reversed. The contributions from regional and local emissions and the influence of atmospheric transport and chemical reactions on the observed concentrations are discussed in a compendium paper.

Mn/V ratio as a tracer of aerosol sulfate transport

Abstract Concentrations of SO 4 2− , Al, V and Mn were determined in airborne particles during July-August 1981 at five sites in New York State: for 6-h intervals at Mayville, Brewerton and Whiteface Mountain and for 24-h intervals at Oneonta and West Haverstraw. Episodic high [SO 4 2− ] were observed during 18–21 and 24–26 July and 1–4 August. Air trajectories showed that during the 18–21 July and 1–4 August episodes peak [SO 4 2− ] coincided with slow-moving air masses which had spent 1 or more days in the midwestern states of Indiana, Michigan, Ohio or Pennsylvania prior to entering New York. During the episodes [SO 4 2− ] decreased from west to east. No significant local sources of SO 4 2− exist at the 6-h sites. All these lines of evidence together show that during these episodes SO 4 2− were transported from the industrial Midwest. During the 24–26 July episode, peak [SO 4 2− ] at Mayville coincided with air masses entering the state from Ohio, but at Brewerton and Whiteface Mountain the highest [SO 4 2− ] occurred when air masses came from metropolitan New York City and the mid-Atlantic states. The average [SO 4 2− ] at Mayville were 2-fold higher than at Brewerton and Whiteface Mountain. The average manganese/vanadium ratio (Mn/V) in aerosols from the Midwest (1–10) has been suggested to be ~ 10 times that in the Northeast ( 4 2− ] were due to transport from the Midwest. On 25–26 July the average Mn/V was high at Mayville (2.8) but low at Brewerton (0.29) and Whiteface Mountain (

40Ar-39Ar age of the Shergotty achondrite and implications for its post-shock thermal history

Analyses of 40Ar-39Ar have been made on a whole rock sample and a maskelynite (feldspar) separate of the shocked Shergotty achondrite. The maskelynite gave a plateau age of 254 ± 10 Myr. The whole rock sample gave a complex release with apparent ages between 240 and 640 Myr. The slightly younger Rb-Sr isochron age of 165 Myr for Shergotty (Nyquistet al., 1978) suggests that the maskelynite as well as the whole rock was incompletely degassed. Reasonable Ar diffusion characteristics for Shergotty for shock heating temperatures of <400°C indicate D/a2 of 10−11−10−13 sec−1. The time required to lose 95% of the 40Ar from the plagioclase would be ~103–104 yr. When this gas diffusion time is introduced into a thermal model of a cooling ejecta blanket of variable thickness, a post-shock cooling time of ≳ 103 yr and a burial depth of ≳ 300 m are indicated for Shergotty. These conclusions are not seriously affected by uncertainties in the thermal model. Most likely the shock event occurred ~ 165 Myr ago, but no earlier than 250 Myr ago, when the Shergotty parent object experienced a collision in the asteroid belt. As a result of that collision, feldspar was converted to maskelynite, the K-Ar and Rb-Sr ages were completely or nearly completely reset, and the Shergotty meteorite was heated to <400°C and left to cool slowly inside the parent body.

Trace element concentrations in summer aerosols at rural sites in New York state and their possible sources

Abstract Eighty five samples of air particulates collected during the summers of 1975–1977 at three rural and one urban sites in New York State were analyzed for up to 13 elements by instrumental neutron activation analysis. Sixteen samples showed high episodic concentrations of several trace elements and sulfate. SO 4 2− , Cr, Zn, As, Se, Br and Sb were distinctly enriched in these aerosols, relative to their crustal abundances. Sc was used as the reference for the crustal component. Episodic and non-episodic events were statistically indistinguishable if only the means and ranges of elemental concentrations and the enrichment factors were considered. However, correlation matrix and factor analysis showed that while non-episodic cases had inexplicably complex factor loading structures, the structure for episodic cases was simple. Episodic events therefore appear to be better indicators of the sources of non-urban aerosols. Five factors were sufficient to account for 87 % of the total variance in the episodic system. When the dependence of the factors on the set of elements was correlated with the elemental emission patterns of probable sources five sources of the trace elements in these aerosols were identified: distant coal-fired power plants (for SO 4 2− , As. Se), refuse incinerators (for Zn, Sb), iron and steel works (for Cr and possibly Fe, Mn). crustal material (for K, Sc, Mn, Fe) and automotive emissions (for Br).

Determination of trace metals in atmospheric aerosols with a heavy matrix of cellulose by microwave digestion-inductively coupled plasma mass spectroscopy

Abstract A microwave digestion method followed by inductively coupled plasma mass spectrometric (ICP-MS) analysis was developed to determine trace metal concentrations in atmospheric aerosol samples with a heavy matrix of cellulose material. A combination of HF–HNO 3 –H 2 O 2 –H 3 BO 3 was used for digestion. The background spectral features contributed by the matrix elements were studied. In particular, spectral and non-spectral interference caused by B and F were investigated. Detection limits of V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Cd, Sb and Pb were determined in the presence of various amounts of matrix elements. In general, the detection limits of most elements degraded with an increase in B and F. Vanadium (V) suffered most due to severe spectral interference from 11 B 40 Ar + and/or 19 F 16 O 16 O. The concentrations of elements in filter paper matrix blanks were measured. An NIST standard (urban particulate matter, 1648), as well as real world atmospheric aerosol samples from Whiteface Mountain, NY, and from Mayville, NY were pressed into pellets with a great amount of cellulose filter material and digested, and the concentrations of trace metals were determined. For the NIST standard, the recoveries of V, Mn, Fe, Co, Ni, Cu, Zn, Cd, As, Sb and Pb were over 90%, while 77 and 70% for Cr and Se, respectively. For the atmospheric aerosol samples from Whiteface Mountain and Mayville, NY, only the values of Fe, Se, As, Sb and Zn could be compared with those obtained through instrumental neutron activation analysis, and the agreement was within ±10%.

Semicontinuous PM2.5 sulfate and nitrate measurements at an urban and a rural location in New York: PMTACS-NY summer 2001 and 2002 campaigns.

Abstract Several collocated semicontinuous instruments measuring particulate matter with particle sizes ≤2.5 μm (PM2.5) sulfate (SO4 22−) and nitrate (NO3 −) were intercompared during two intensive field campaigns as part of the PM2.5 Technology Assessment and Characterization Study. The summer 2001 urban campaign in Queens, NY, and the summer 2002 rural campaign in upstate New York (Whiteface Mountain) hosted an operation of an Aerosol Mass Spectrometer, Ambient Particulate Sulfate and Nitrate Monitors, a Continuous Ambient Sulfate Monitor, and a Particle-Into-Liquid Sampler with Ion Chromato-graphs (PILS-IC). These instruments provided near realtime particulate SO4 2− and NO3 − mass concentration data, allowing the study of particulate SO4 2−/NO3 − diurnal patterns and detection of short-term events. Typical particulate SO4 2− concentrations were comparable at both sites (ranging from 0 to 20 μg/m3), while ambient urban particulate NO3 − concentrations ranged from 0 to 11 μg/m3 and rural NO3 − concentration was typically less than 1 μg/m3. Results of the intercomparisons of the semicontinu-ous measurements are presented, as are results of the comparisons between the semicontinuous and time-integrated filter-based measurements. The comparisons at both sites, in most cases, indicated similar performance characteristics. In addition, charge balance calculations, based on major soluble ionic components of atmospheric aerosol from the PILS-IC and the filter measurements, indicated slightly acidic aerosol at both locations.

Composition of aerosols and cloud water at a remote mountain site (2.8 kms) in Pakistan

Major ion and trace metal concentrations were determined in aerosols and cloud water at a site in the Himalayan Mountains of Northern Pakistan. In spite of the fact that the site is well removed from significant urban/industrial pollution sources the SO2−4 concentrations in some of the samples were as high as those observed in North America. Concentrations of Se, Tl, Pb, Cl, Cd, Sb, Zn, and As in aerosols were highly enriched relative to average crustal abundances indicating significant anthropogenic contributions. Cloud water concentrations of major ions and trace elements are reported for 18 samples from six different clouds. The pH varied between 5.3 and 6.8 in spite of the fact that the SO2−4 concentration approached 300 μmol in some samples, values often observed in the northeastern US. Selenium was used as a tracer to determine in-cloud production of SO2−4 in these clouds and in three of the six clouds 40–60% of the observed SO2−4 came from in-cloud production.

Anatomy of an episode of high sulfate concentration at Whiteface Mountain, New York

Abstract Concentrations of seven metals and sulfate in aerosols collected at Whiteface Mountain, New York, were measured continuously in 6-h intervals for 2 weeks in June 1979. Thirteen consecutive samples showed high episodic concentrations of sulfate, Fe, Al and, to a lesser extent, Zn, Pb, K, Mg and Ca. The trajectories for the period of elevated [SO 2− 4 ] passed through the midwestern United States and entered New York State from the southwest. The trajectories for the time periods of low [SO 2− 4 ] before and after the episode entered New York from the north. This relationship between high concentrations and the surface-air trajectories suggests that in this particular episode SO 2− 4 and metals may have been transported from the Midwest. As the effective travel time ( T ) of this air mass, passing through a high SO 2 -emission area, increased, [SO 2− 4 ] increased, while the metal concentrations (particularly [Fe]) decreased. These observations suggest that in this episode Fe and SO 2− 4 were transported together. Analyses of other episodes are needed before any general conclusions can be drawn. This analysis could not have been performed with 24-h sample collection periods and therefore illustrates the advantages of relatively short collection times.

Identification of submicrometer coal fly ash in a high-sulfate episode at Whiteface Mountain, New York

Abstract The most direct evidence yet of a coal-burning source of a high-sulfate air mass reaching the Northeast has been detected in a brief episode at Whiteface Mountain, NY, on 23 June 1983. Individual microparticles were characterized by electron microscopy in three samples from this period: 12 h before the SO2−4 peak ( [SO 2− 4 ] = 2.7 μg m −3 ), during the peak (24 μg m −3) and 12 h after the peak (2.2 μg m −3). This analysis provided the first confirmation of the association of coal fly ash and high [SO2−4] at a rural acid-stressed site. Common at the time of peak [SO 2−4] were sub-μm magnetite and glass spheres as identified by morphology, elemental composition and mineralogy. This coal fly ash was essentially absent 12 h before or 12 h after the episode. A midwestern source of this episode was indicated by Mn/V ratios and by meteorologic conditions.

Field and Laboratory Evaluation of the Thermo Electron 5020 Sulfate Particulate Analyzer

The Thermo Electron Model 5020 Sulfate Particulate Analyzer is a recently commercialized instrument that provides continuous measurements of the sulfate component of ambient particulate matter. The technique uses a stainless steel rod placed inside a quartz oven to reduce the particle sulfate to sulfur dioxide; followed by pulsed fluorescence detection of the sulfur dioxide. Field and laboratory evaluations of a pre-production version of the analyzer are described as well as laboratory evaluations of the pre-production version and two production units. Laboratory tests concentrated on challenging the instruments with ammonium sulfate aerosol, but tests with sodium, potassium, and calcium sulfate are reported as well. The instrument performed very well in field and laboratory settings, reporting values that were highly correlated with continuous mass measurements in the lab, and 24-hour filters in the field. Conversion/detection efficiencies for ammonium sulfate in the laboratory, and for ambient sulfate aerosol at our rural site in Addison, New York, were both very close to 80%. Laboratory conversion efficiencies for calcium, sodium, and potassium sulfate salts ranged from 4% to 63%. These lower efficiencies for mineral-type sulfates will be an important consideration in areas with significant concentrations of sea salt or mineral dust sulfate, and less important for the high sulfate Eastern US which is dominated by ammonium sulfate.